Serial transmission has been increasingly used for high-speed transfer of signals within an information processing apparatus or between an information processing apparatus and a peripheral device. Typical standards for such high-speed serial transmission include Peripheral Component Interconnect Express (PCI Express) (hereinafter abbreviated as PCIe) and serial-attached Small Computer System Interface (SCSI), called SAS.
Interface circuits based on the high-speed serial transmission standards described above execute a training sequence for optimizing settings when connection is initiated. For example, the SAS standard defines a test signal pattern for training and a message for requesting the partner to increase or decrease a setting value of a parameter.
Techniques for optimization of a parameter are as follows. For example, a technique has been proposed in which hard disk drive (HDD) mounting position information and HDD identification information are matched with a transmission optimization parameter table to determine a data transmission parameter so that an optimal transmission function can be set for each HDD.
There has also been proposed a technique for optimization of a parameter used for data transfer, in which even when a high-speed serial bus is applied to data communication devices having complex operation modes, a parameter used for data transfer in each traffic, such as a packet size, is adjusted so that a transfer rate of each traffic present between data communication devices connected via a high-speed serial bus has a preset target value.
Japanese Laid-open Patent Publication No. 2006-221271 and Japanese Laid-open Patent Publication No. 2008-021024 are examples of related art.
A transmit-side SAS interface receives a message for requesting an increase or decrease in a setting value of a parameter, as described above, from the receive side and negotiates with the receive side to optimize a parameter for setting a signal transmission characteristic. However, a setting value determined by a negotiation may not always be optimal depending on the conditions such as the length of the transmission path, and even the use of a setting value determined by a negotiation may result in the occurrence of a communication failure. A PCIe interface may also experience a similar issue.
It is therefore desirable to provide an information processing apparatus, a storage system, and a computer-readable non-transitory storage medium storing a communication control program with improvement in communication stability.